code: def _get_tester():
      global tester
      if tester is None:
          tester = ImageTester()
      return tester
  
imports: import time
  import os
  import sys
  import inspect
  import base64
  from subprocess import check_call, CalledProcessError
  import numpy
  from http.client import HTTPConnection
  from urllib.parse import urlencode
  from ..None import scene, config
  from ..io import read_png, write_png
  from ..gloo.util import _screenshot
  from ..util import run_subprocess
  from .None import IS_CI
label_desc: Use image node_id 1 for calling a global function with example usage: _get_tester() and returns: tester